In recent years, electronic devices such as an audiovisual device, a personal computer, and a portable communication device are quickly made portable or cordless, and a nickel cadmium storage battery, a nickel metal-hydride storage battery, a lithium rechargeable battery and the like are used as a driving power source of the electronic device because these batteries are reliable and easy to maintain. Electrode plates used in such a battery as a positive electrode plate and a negative electrode plate are obtained by cutting a strip-shaped electrode plate material which is made of a base material having a three-dimensional frame such as a three-dimensional metal porous material or expanded metal filled or coated with an active material into a predetermined length.
In a conventional method for cutting an electrode plate material, however, since the electrode plate material is made of a base material having a three-dimensional frame filled or coated with an active material, when the electrode plate material is cut in a state that a flat cut die makes contact with the front face of a portion of the electrode plate material to be cut on both front and rear sides, wastes generated during cutting are crimped on the surface of the electrode plate after cutting by the cut die. Also, cutting leaves a cut burr and a curling burr is generated during returning a blade due to the contact between the electrode plate material and the cut die. If an electrode plate having such a generated burr is installed in a battery, the cut burr on a cutting plane of the electrode plate, for example, a positive electrode plate penetrates through a separator and directly makes contact with a negative electrode plate and hence causes a serious short circuit. In particular, a cut burr extending in parallel with the cutting plane has the high possibility of causing a short circuit. Therefore, when the electrode plate material is cut, it is extremely important to prevent the cut burr from being generated on the cutting plane in order to preclude the major cause of a short circuit of a battery and stabilize the quality of the battery.
Accordingly, to cut an electrode plate material while restraining the generation of the above-mentioned cut burr, a method for cutting an electrode plate material was conventionally proposed by which a pair of cut dies sandwiches and fixes the vicinity of each of both sides of a portion of the electrode plate material to be cut and then the pairs of cut dies are moved oppositely each other in the direction of the thickness of the electrode plate material (refer to, for example, Patent Document 1). Patent Document 1 also proposes a cutting method by which the thickness of the portion of the electrode plate material to be cut and the vicinity of both sides thereof are formed thinner than the other portions. When the electrode plate material is cut, a pair of cut dies sandwiches and fixes each of the both sides of the portion formed thinner and then the pairs of cut dies are moved oppositely each other in the direction of the thickness of the electrode plate material.
As another method for cutting an electrode plate material while restraining the generation of a cut burr, there is known a method passing through a process in which after the electrode plate material is cut with a die for cutting processing, an inside stripper provided inside of a blade and a lifter composing a part of a bottom die sandwich the cut electrode plate on both of front and rear sides while applying proper pressurizing force in a state where both of the blade and an outside stripper composing a top die presses the outside of a cut portion of the electrode plate material against the top face of an anvil, and the electrode plate material is once pressed into the inside of the blade at a predetermined distance and then is brought back toward a tip of the blade (refer to, for example, Patent Document 2).    [Patent Document 1] Japanese Patent Laid-Open Publication No. 2001-319644    [Patent Document 2] Japanese Patent Laid-Open Publication No. 2002-126828